Process for preparing improved plastic compositions and the resulting products

ABSTRACT

Plastics having improved impact resistance are prepared by interpolymerizing a mixture including a rubbery interpolymer of ethylene, at least one alpha monoolefin having 3-16 carbon atoms and an alkylidene norbornene, preferably 5-ethylidene-2norbornene and an alkenyl aromatic monomer such as styrene, a vinyl or vinylidene halide such as vinyl chloride, an acrylic monomer such as acrylonitrile, and mixtures thereof in an organic solvent for the rubbery polymer and in the presence of a free radical catalyst.

United States Patent 151 3,683,050 Meredith et al. 1451 Aug. 8, 1972[54] PROCESS FOR PREPARING [56] References Cited IMPROVED PLASTICCOMPOSITIONS AND THE RESULTING PRODUCTS UNITED STATES PATENTS [72]Inventors: Cums L. Meredith Baton Rouge, 3,271,477 9/1966 Kresge..260/878 La. Robert E Bane Bamn 3,408,424 10/1968 Barkhofi ..260/878Rollge La w'iuim A Bishop 3,483,273 12/1969 Procnal etal ..260/878 Batonk La 3,489,821 1/1970 Witt et a1 ..260/876 3,489,822 1/1970 Witt et a1..260/878 [73] Assignee: Copolyme Rub er Chemica 3,538,192 11/1970Bishop ..260/878 Corporatio B on ouge La- 3,435,096 3/1969 Limvertetal...260/878 [22] Filed: April 1969 Primary ExaminerSamuel H. Blech [21]Appl. No.: 819,127 Assistant Examiner-Helen W. Roberts Related us.Application Data Attorney-McDougall, Hersh, Scott & Ladd [63]Continuation-in-part of Ser. No. 709,902, ABSTRACT March 4, 1968, Pat.No. 3,538,190, which is a Plastics havin d g improve impact resistanceare commuatmn'mpan of 626,930 prepared by interpolymerizing a mixtureincluding a March 1967' 3,538,191- rubbery interpolymer of ethylene, atleast one alpha monoolefin having 3-16 carbon atoms and an alky- [52]US. Cl ..260/876 R, 260/33.6 UA, [idem norbomene preferably 5 ethydene 2nrbor 260/33'8 UA260/45'7 PZ6OIS78R nene and an alkenyl aromatic monomersuch as IIILCI ..C08I 37/18,C08f4l/l2 styrene a vinyl or vinylidenehalide h as i l Field of Search ..260/878 R, 876 R chloride, an acrylicmonomer such as acrylonitrile, and mixtures thereof in an organicsolvent for the rubbery polymer and in the presence of a free radicalcatalyst.

9 Claims, No Drawings PROCESS FOR PREPARING IMPROVED PLASTICCOMPOSITIONS AND THE RESULTING PRODUCTS This application is acontinuation-in-part of our copending application Serial'No. 709,902,filed March 4, 1968, and entitled Process for Preparing improved PlasticCompositions and the Resulting Products, now US. 3,538,190, whichapplication is a continuation-inpart of copending application Serial No.626,930,filed March 30, 1967 for Process for Preparing Improved PlasticCompositions and the Resulting Products, now US. 3,538,191.

This invention broadly relates to the preparation of plastics havingimproved impact resistance. The invention further relates to novel highimpact plastic compositions containing a specific rubbery polymer whichimpartsimproved properties.

A wide variety of processes have been proposed heretofore for preparinghigh impact or-gum plastic compositions, which are referred to herein-asbeing rubber modified plastics. The most commonly used commercialprocess involves a number of steps, reactions, and treating vesselsincludingpreparing a hard and durable styrene-acrylonitrile resinwhichis brittle and has low impact resistance, preparing in anotherreaction vessel a highly unsaturated elastomer such as polybutadienewhich is capable of absorbing shock, thereafter improving thecompatability of the elastomer with the styrene-acrylonitrile resin bygrafting monomeric styrene and acrylonitrile thereon, and then blendingthe styrene-acrylonitrile resin with the grafted elastomer inproportions to arrive at a product which has useful physical properties.Often the prior art process failed to produce a rubber modified plastichaving optimum properties in all respects, including processingcharacteristics, impact resistance, tensile strength and hardness.

A simplified process for the preparation of rubber modified plastics inwhich the resinous polymer and the grafted rubbery polymer are preparedsimultaneously from the resin-forming monomer or monomers and theungrafted rubbery polymer would be highly desirable. Such a processcould be carried out in a single reaction vessel and other reactions orblending steps would not be necessary. However, an entirely satisfactoryprocess of this type was not available prior to the present invention.

It is an object of the present invention to provide a novelpolymerization process for the preparation of rubber modified plasticsin which the resinous polymer and the rubbery polymer grafted with theresin-forming monomers may be prepared simultaneously.

It if still a further object to provide rubber modified plastics havingimproved properties.

Still other objects and advantages of the invention will be apparent tothose skilled in the art upon reference to the following detaileddescription and the examples.

In practicing the present invention, rubber modified plasticcompositions are prepared by interpolymerizing a rubbery polymer and oneor more alkenyl aromatic monomers, vinyl or vinylidene halides, and/orone or more acrylic monomers, in an organic solvent for the rubberypolymer, and in the presence of a free radical catalyst. It isunderstood that there are certain preferred variants which produceimproved results, as will be described more fully hereinafter.

- tion is especially useful for the -naphthalene,-naphthalenesubstituted with one or more alkyl groups containing 1-4 carbon atomssuch as alpha-methyl or beta-methyl naphthalene and their higherhomologs, paraffin an cycloparaffin hydrocarbons containing 5-15 carbonatoms, and preferably 6-l0 carbon atoms, such as pentane, n-hexane, 3-methylpentane, Z-methylpentane, 2,2- and 2,4- dimethylpentane, heptane,cyclopentane, cyclohexane, and alkyl substituted cyclopentanes andcyclohexanes wherein the alkyl group or groups contain l-4 carbon atoms,including methyl cyclopentane, methyl cyclohexane and their homologs.The halogenated derivatives of the above solvents may be employed, andespecially the chlorine and bromine derivatives. Chlorobenzene is veryuseful as a solvent.

Mixtures containing two or more of the foregoing solvents may be used,and are preferred in many instances. Examples of solvent mixtures whichgive unusually good results include one or more aromatic components suchas benzene, toluene, xylene and/or ethyl benzene, and one or moreparaffin or cycloparaffin hydrocarbon components containing six througheight carbon atoms such as n-hexane, 3-methylpentane, Z-methylpentane,n-heptane, methyl hexanes, n-octane, methyl octanes, methylcyclopentane,and/or cyclohexane.

Usually better results are obtained when the above solvent mixturescontain about 40-60 percent by weight of the aromatic solvent component,and about 60-40 percent by weight of the paraffin or cycloparaffinhydrocarbon .component. Best results are usually obtained when about 50percent by weight of each component is present.

The alkenyl aromatic monomers which may be used in practicing thepresent invention include alkenyl aromatic hydrocarbons containing 8-20carbon atoms and their halogenated derivatives. Specific examplesinclude styrene, chlorostyrene, alpha-alkyl styrenes wherein the alkylgroup contains 1-8 carbon atoms such as alpha-methyl styrene,alpha-chloro styrene, vinyl naphthalene, alkyl substituted vinylnaphthalenes wherein the alkyl group or groups contain 1-8 carbon atoms,and halogen substituted vinyl naphthalenes. Styrene is preferred in mostinstances, and the invenpreparation of high impact polystyrene.

The vinyl or vinylidene halides, hereinafter included ,within thealkenyl aromatic monomer, which may be used as monomers include vinylfluoride, vinyl wherein R is selected from the group consisting ofhydrogen and alkyl groups having 1-5 carbon atoms, and X is selectedfrom the group consisting of wherein R is an alkyl group containing l-9carbon atoms. Examples of specific acrylic monomers which are especiallyuseful include acrylonitrile, acrylamide, methyl or ethyl acrylonitrile,and acrylic, methacrylic, and ethacrylic acid and the methyl, ethyl,propyl and isopropyl esters thereof. Acrylonitrile is usually thepreferred acrylic monomer.

When a mixture of one or more of the alkenyl aromatic monomers and oneor more of the acrylic monomers is employed, preferably the ratio byweight of alkenyl aromatic monomer to acrylic monomer is at least 1.5:1,and between 2:1 and 4:1 for better results. The optimum properties areobtained in many instances with styrene and acrylonitrile at ratios byweight of 67:33 to 78:22, or about 2.5: l. The preferred monomers foruse in preparing the monomer mixtures are usually styrene andacrylonitrile.

The rubbery polymer component are products resulting frominterpolymerizing a monomeric mixture containing -90 mole percent ofethylene, 10-90 mole percent of at least one other straight chain alphamonoolefin containing 3-16 carbon atoms which preferably is propylene,and 0.1-10 mole percent of an alkylidene-Z-norbomene, and especiallyS-ethylidene- 2-norbornene, in solution in hexane or other organicpolymerization solvent, and in the presence of a catalyst prepared fromvanadium oxytrichloride and methyl or ethyl aluminum sesquichloride orother suitable Ziegler catalyst.

It is preferred that the elastomers having low unsaturation be preparedfrom a monomeric mixture containing ethylene, propylene and thealkylidene-Z-norbornene, in proportions to produce a polymer having goodelastomeric properties and an unsaturation level of at least twocarbon-to-carbon double bonds per thousand carbon atoms in the polymer.For example, the elastomer may contain chemically bound therein molarratios of ethylene to propylene varying between about 80:20 and :80, andbetween 70:30 and 55:45 for better results. The alkylidene-Z-norbornenemay be chemically bound therein in an amount to provide an unsaturationlevel of 2-25, and preferably about 3-16 carbon-to-carbon double bondsper thousand carbon atoms .1 the polymer.

Examples of alkylidene-2-norbomenes which may be used include5-alkylidene-2-norbornenes wherein the alkylidene group contains l-2Ocarbon atoms and preferably l-8 carbon atoms. Specific examples such asalkylidene-Z-norbornenes include 5-ethylidene-2- norbornene,5-isopropylidene-Z-norbornene, S-butylidene-2-norbornene,5-pentylidene-2-norbornene; 5- propylidene-Z-norbornene and the like.The elastomers prepared from ethylene, at least one monoolefincontaining 3-16 carbon atoms, and the 5-alkylidene-2-norbomenes, whereinthe alkylidene group contains l-20 and preferably l-8 carbon atoms,produce novel rubber modified plastics which have exceptionalproperties. The elastomer prepared from 5-ethylidene-2- norbomene ismuch preferred as it has outstanding properties and produces manyunusual and unexpected results when used as the elastomer in the plasticcompositions of the invention. As a result, this elastomer is in a classby itself.

A wide variety of free radical polymerization catalysts may be employed,including those used in the prior art processes for preparing highimpact polystyrene and styrene-acrylonitrile plastics. ln some instance,the hydroperoxide groups that are formed by oxidation of the rubberycomponent may act as the free radical catalyst. Examples of free radicalpolymerization catalysts include the organic peroxides such as benzoylperoxide, lauroyl peroxide, propionyl peroxide, 2, 4-dichlorobenzoylperoxide, acetyl peroxide, tertiary butyl hydroperoxide, paramenthanehydroperoxide, tertiary butyl perbenzoate, tertiary butylperoxyisobutyrate, and dicumylperoxide. Mixtures of one or more of theabove or other peroxides and hydroperoxides may be employed.Additionally, mixtures of one or more peroxides and/or hydroperoxideswith azo-bisdiisobutyronitrile give better results in the someinstances, and especially where a less active catalyst is effective. Forexample, when sing the highly unsaturated diene rubbers, or rubbers oflow or high unsaturation that have been subjected to an oxidation stepto form hydroperoxide groups thereon, then a less active free radicalcatalyst should be used for optimum results. The catalyst mixture maycontain 25-75 percent and preferably about 50 percent by weight of theazobisdiisobutyronitrile, and -25 percent, and preferably about 50percent by weight, of one or more of the above organic peroxides. Ininstances where an unoxidized elastomer is used having a low degree ofunsaturation, then it is desirable to employ a highly active freeradical initiator, e.g., a prior art initiator which is known toabstract hydrogen from the elastomer and rapidly catalyze the graftreaction. Many examples of such highly active free radical initiatorsare known, such as benzoyl peroxide.

The amount of the alkenyl aromatic monomer and/or the acrylic monomerthat is grafted on the elastomer during the polymerization step shouldbe sufficient to provide a desirable, and preferably an optimum, degreeof compatibility with the resin that is formed simultaneously. Forexample, the resin-forming monomer or monomers may be grafted on theelastomer in an amount to provide a ratio by weight of the graftedmonomeric material to the elastomer between l:4 and 4:1, and preferablybetween 1:4 and 2:1. The best results are usually obtained when about30-120 parts by weight of the resin-forming monomer or monomers aregrafted on each parts by weight of the rubbery polymer.

The reaction mixture to be polymerized should contain about l-50 partsby weight, and preferably 4-25 parts by weight, of the rubbery polymerfor each 99-50 parts by weight, and preferably 96-75 parts by weight, ofthe alkenyl aromatic monomer and/or the acrylic monomer. The monomericmaterial may be one or more alkenyl aromatic monomers, or one or moreacrylic monomers, or a mixture thereof in the ratios previouslymentioned. The reaction mixture thereof should contain about O.252.5parts by weight, and preferably 0.5-1.3 to 0.75-l.l parts by weight ofthe free radical catalyst or initiator for each 100 parts by weight ofresin-forming monomer or monomers. The reaction mixture may containabout 35-90 percent by weight, and preferably 50-75 percent by weight,of solvent based on the total weight of reaction mixture. Additionally,much better results are achieved when the organic solvent content of thereaction mixture is varied between not less than 35 percent andpreferably not less than 50 percent by weight of the total weight of thereaction mixture at the lower limit of the rubbery polymer contentmentioned above, and not more than 90 percent and preferably not morethan 75 percent by weight thereof when the upper rubbery polymer limitis used. When the preferred rubbery polymer range mentioned above isused, i.e., 4-25 percent by weight, then the solvent should be presentin an amount of about 85-60 percent by weight of the total reactionmixture. It is understood that the solvent is always present in anamount to dissolve the rubber and form a solution thereof at the time ofcommencing the reaction, and

especially when an EPDM rubber is employed.

The temperature of the polymerization may vary over wide ranges. Forinstance, reaction temperatures of approximately 30-l50 C., andpreferably about 60-80 C. with certain catalysts such as benzoylperoxide, are usually satisfactory. The polymerization is continued fora sufficient period of time to assure a desired percent conversion ofthe monomer or monomers. This will vary somewhat with the specificcatalyst, solvent, rubbery polymer, monomers, and reaction temperaturethat are employed. However, reaction times of about 4-24 hours areusually satisfactory. In any event, preferably the reaction is continueduntil at least 60 percent by weight of the monomeric material initiallypresent has been converted to polymer, and for best results 85-100percent by weight. The amount of monomeric material converted to polymermay be determined by volatilizing the volatile monomeric components ofthe reaction mixture, weighing the nonvolatile components andcalculating the percent by weight conversion therefrom.

The reaction mixture also may contain a crosslinking agent, i.e., acompound containing at least two reactive sites such as two or moreethylenic double bonds. Examples of cross-linking agents aredivinylbenzene, divinyl ether of diethylene glycol, triallylcyanurate,and

l,3-butylene-dimethacrylate. The crosslinking agent may be added in anamount of, for example, 0.005-l.0 parts by weight, and preferably about0.01 to 0.5 parts by weight, per 100 parts by weight of the monomericmater .l to be polymerized. Still other types of crosslinking agents maybe employed as it is only necessary that it have two or more reactivesites under the conditions of the polymerization.

The reaction mixture may be agitated during the polymerization butvigorous agitation is not necessary. As the polymerization proceeds, theresinous polymer that is formed generally precipitates in a finelydispersed form and remains suspended in the reaction mixture. Therubbery polymer generally remains dissolved in the solution after it hasbeen grafted with the resin-forming monomers. Thus, the polymerizationmay produce simultaneously one or more resinous homopolymers of themonomer or monomers present, a resinous interpolymer when two or moreresin-forming monomers are present, and the rubbery polymer grafted withone or more of the resin-formin g monomer or monomers. As a result, atthe end of the polymerization the reaction mixture contains all of thecomponents that are needed for a high impact plastic composition, and itis only necessary to recover the products of the polymerizationtherefrom.

The preceding discussion has been concerned largely with polymerizationwithout incremental addition of solvent and/or initiator during thecourse of the reaction. In accordance with still further preferredvariants of the invention, a mixed aromatic-aliphatic solvent such asbenzene-hexane is employed in combination with incremental addition ofthe solvent alone, incremental addition of the initiator alone,incremental addition of solvent and initiator, or incremental additionof a solvent component so that the relative amount of the aromaticcomponent is decreased as the polymerization proceeds, with or withoutincremental initiator addition. While each of the above techniques ofincremental addition offer advantages over polymerization withoutincremental addition, the incremental addition of solvent and initiator,and preferably with a change in the aromatic-aliphatic solvent ratio sothat the aromatic component is decreased as the polymerization proceeds,produces the best results.

When the ratio of the aromatic and aliphatic solvent components is notchanged during the polymerization, then the weight ratio of the aromaticcomponent to the aliphatic component should be between about 60:40 and40:60, and preferably about 50:50 for better results. When incrementaladdition of solvent is practiced, then the weight ratio of aromatic toaliphatic solvent may be between 65:35 initially and 35:65 at the end ofthe polymerization, and preferably between 60:40 initially and 40:60 atthe end of the polymerization. The total amount of solvent in thereaction mixture at the end of the reaction need not differ from thatpreviously mentioned, i.e., it may be 35-80 percent by weight of thetotal weight of the reaction mixture, and preferably 50-75 percent byweight.

The total amount of initiator that is added in the incremental additiontechnique need not differ from the quantity normally employed; however,usually the initiator is more efficient and thus smaller quantities maybe used. This reduces the overall cost and is preferred.

The weight percentages of initiator and/or solvent that are added duringthe course of the polymerization are fractional amounts of thequantities present in the final reaction mixture. The fractional amountsof initiator added by incremental addition may be 0-75 percent, andpreferably 20-50 percent by weight of the total. The amount of solventadded by incremental addition may be 0-50 percent, and preferably 20-40percent of the total weight of solvent in the final reaction mixture.

In instances where benzoyl peroxide is the initiator, the reactiontemperature may be 68-85 C., and preferably 72-82 C. For otherinitiators, better results are obtained when the reaction temperaturelimits are selected so that the initiator half-life is between 2 and 13hours.

The time interval or intervals at which solvent and/or initiator areadded are determined primarily by the amount of initiator to be addedafter the start of the reaction and by the reaction temperature. Athigher reaction temperatures, it is desirable that the addition be madelater in the reaction and multiple additions are often preferred. Thetime of making the addition may be between one-seventh and six-seventhsof the total reaction time that is necessary to achieve at least 90percent by weight conversion of the monomers. A plurality of incrementaladditions may be made, such as 25 or more.

The incremental addition technique may be used very effectively in acontinuous polymerization wherein a series of reactors is employed, withthe polymerization being carried out to a desired degree of conversionin the first reactor, the resulting reaction mixture then passed to thesecond reactor, and so on through the series. Incremental addition ofsolvent and/or initiator may be made to one or more reactors to therebyachieve optimum properties in the reinforces plastic product which iswithdrawn from the final reactor in the series. Reaction conditions suchas temperature, pressure, concentrations and ratios of reactants mayalso differ from reactor to reactor. By way of example, in a continuouspolymerization using two reactors, benzoyl peroxide as a catalyst, and amixture of styrene and acrylonitrile as the monomers, the first reactormay be operated at a temperature of 7278 C. until 10-30 percent byweight of the monomer content is converted to polymer the partiallypolymerized mixture is passed to the second reactor, and thepolymerization is continued until 10-95 percent by weight of the monomercontent is converted to polymer, and preferably at a higher reactiontemperature such as 75-82 C. which assures faster and more completepolymerization.

Incremental addition has a number of beneficial effects such as a higherIzod impact strength in the product, a better balance of Izod impactstrength and flow properties, a more efficient utilization of theinitiator, and a much faster reaction time which may be reduced to aslittle as 6 hours, as compared with the usual 12-14 hours for at least90 percent by weight conversion of the monomers to polymer. A number offurther advantages are obtained when the ratio of aromatic component toaliphatic component in the solvent is relatively high during the initialstages of the reaction, and is decreased during the polymerization.

The plastic composition may be recovered from the reaction mixture bycoagulation with a lower alcohol such as methyl, ethyl or isopropylalcohol, by flashing off the solvent, or by anextrusion-devolatilization step. When ne product is recovered byflashing the solvent, preferably the reaction mixture is passed into avessel containing boiling water. Steam is supplied to the vessel and thesolvent evaporates and is removed overhead as a vapor, together with anyfree monomer content. The plastic product is recovered as a solid inparticulate form, and it may be dewatered, washed in water to removewater soluble impurities, and dried in a prior art oven at 50-l00 C.until the water content is removed. F luidized bed drying at 50-l00 C.also may be used in most instances with good results. The dried plasticcomposition may be pelletized or formed into other desirable shapessuitable for marketing.

Prior art antioxidants, processing aids, and other compoundingingredients and aids may be added at any convenient point in theprocess. Inasmuch as these ingredients are soluble or dispersible in theorganic solvent, they may be added to the polymerization mixture and maybe dissolved or dispersed therein prior to recovery of the product.Examples of suitable antioxidants include phosphited polyalkylpolyphenols and tri (mixed monononyl-dinonyl) phenyl phosphite. Examplesof processing aids are mineral oils and the salts and esters of higherfatty acids. When desired, coloring agents may be added to producecolored resins. The coloring pigments of the prior art are suitable forthis purpose.

The high impact plastic compositions prepared by the process of theinvention have better physical properties such as impact resistance,hardness and tensile strength than similar products of the prior art.Additionally, by using the preferred rubbery polymers of the inventionhaving low unsaturation such as the terpolymers of ethylene, propyleneand S-alkylidene-Z- norbornene, even better physical properties may beobtained. The novel plastic composition of the invention comprises (A) aresinous polymer, which may be one or more homopolymers of the alkenylaromatic monomers or one or more interpolymers of the alkenyl monomersand acrylic monomers, and (B) a graft interpolymer of l) a rubberyinterpolymer of ethylene, at least one alpha monoolefin containing 3-16carbon atoms, and 5-alkylidene-2-norbornene, and (2) monomeric materialwhich may be one or more alkenyl aromatic monomers or acrylic monomers,or mixtures thereof. The alkylidene group contains 1-8 carbon atoms, andthe preferred species is 5-ethylidene-2-norbornene. High impact plasticsprepared from terpolymers of ethylene, propylene and 5-ethylidene-2-norbomene have a good balance of properties and many unusual andunexpected properties including a high heat distortion temperature, anability to be processed repeatedly without degradation, a unique degreeof platability, high Izod impact values, a high melt flow activationenergy, and an exceptional resistance to falling dart impact. Thecombination of a high heat distortion valve and good processingcharacteristics is most unusual. The preferred 1 for use in preparingthe above products are styrene, or styrene and acrylonitrile. The novelplastic compositions may contain the ratios of components previouslymentioned, and may be prepared by the process of the invention using theratios of reactants previously mentioned.

The foregoing detailed description and the following specific examplesare for purposes of illustration only, and are not intended as beinglimiting to the spirit or scope of the appended claims.

EXAMPLE I This example illustrates the preparation of a rubber modifiedpolystyrene by the process of the invention. The terpolymer was aninterpolymer of ethylene, propylene, and 5-ethylidene-2-norbornene whichcontained chemically bound therein approximately equal weights ofethylene and propylene, and sufficient 5- ethylidene-Z-norbomene toprovide an unsaturation level of 8.7 carbon-to-carbon double bonds per1,000 carbon atoms. The Mooney value was 66 (ML-4).

5.5 grams of the rubbery terpolymer was dissolved in 49.5 grams ofhexane and charged to a laboratory au- 98 percent by weight of thestyrene had reacted.

The product was precipitated from the reaction mixture by addition ofalcohol. The solid product was dewatered, washed in water to removewater soluble impurities, dried and tested. The resulting rubbermodified polystyrene had a Rockwell hardness of 102 (R scale) asdetermined by ASTM D 785 65, Procedure B.

A sample of the product was molded, and then aged for 66 hours at 120 C.No discoloration was observed. Three commercial high impact polystyreneswhich contained a diene rubbery component were tested under the sameconditions and discolored badly.

EXAMPLE ll This example illustrates the preparation of high impactstyrene-acrylonitrile plastics by the process of the present inventionusing a variety of mixed solvent systems, and amounts of rubbery polymerof Example I. All ratios and percentages mentioned in this example arecalculated by weight, and the weights are given in grams.

The rubbery polymer was dissolved in solvent. The reaction vessel wascharged with the solvent mixture and rubbery polymer, and the styreneand acrylonitrile monomers were charged in a weight ratio of styrene toacrylonitrile of 3: 1. benzoyl peroxide was added as the catalyst, andthe temperature was raised to 70 C. to initiate the reaction. Thereaction was continued at 70 C. over a 20 hour period with agitation.This resulted in substantially 100 percent by weight conversion of thestyrene and acrylonitrile monomers to polymer for all runs with theexception of Run No. 2, where the conversion was 96 percent by weight.

The resulting high impact styrene-acrylonitrile plastic was precipitatedfrom the reaction mixture by addition of isopropyl alcohol. The productprecipitated in the form of small particles, which were collected,washed with water to remove water soluble impurities and dried. Theplastic products were tested for tensile strength, Rockwell hardness (Rscale), and Izod impact resistance. Conventional test procedures weredetermined by ASTM D 785-65, Procedure B, the Izod impact resistance wasdetennined by ASTM D 256-56,

Method A, and the tensile strength was determined by ASTM D 638-611. Thedata thus obtained are recorded in Table 1.

It is apparent from the data in Table I that excellent high impactplastics are produced by the one-step process of the invention.

EXAMPLE III This example presents data for the purpose of comparing thephysical properties of the rubber modified plastics of the presentinvention with those of the prior art.

Three of the best commercially available acrylonitrile-butadiene-styrene(ABS) high impact plastics were purchased which had rubber contents of5.5, 10.7 and 15.0 percent by weight, respectively. The rubber contentin each instance was polybutadiene.

Three plastics were prepared by the general procedure of Example 11which had rubber contents of 5.5, 10.7 and 15.0 percent by weight,respectively. The rubber in each run was a terpolymer of ethylene,propylene and 5-ethylidene-2-norbornene.

The above six plastics were tested to determine the Rockwell hardness (Rscale) and Izod impact resistance by the methods of Example 11. The datathus obtained are compared in Table II. It is apparent from these datathat the one step process of the invention produces plastics havingbetter properties than the best commercially available products.

This example illustrates the preparation of rubber modified plasticswithout incremental addition of initiator or a benzene-hexane solvent,with incremental addition of benzene-hexane solvent but withoutchangused in each instance. The Rockwell hardness was mg the ratio ofthe solvent components, incremental TABLE I Rubber Styrene Izod 1munsat- Rubber aeryloni- Rockwell pact resisuration, in plastic trile,Benzoyl hardness tanee it. Tensile Rubber C=C/1,000 (wt. grams (3/1peroxide lbs/in. of strength, Run N0. Solvent composition grams C.percent) ratio) grams scale) notch p.s.i.

170 g. toluene 1 l i ig 15. 0 12. 0 10. 4 1:10 1. 30 104 6.30

105 g. e 1 oro enzene... 2 gmmnn 20.0 12. 0 11. 2 10s 1. 05 101 3.15

175 g. 0nzcne a humane 20.0 12. 0 10. s 105 1. 05 101 3. 07

g. b0nz0ne- 4 105 g. hexane 20. 0 12.0 10.8 1. 65 07 4.54

105 g. cyelohexano. g. benzene s g 0. 0 9. s 5.1 104 1. 04 117 0. 02 s,700

170 g. enzene a gmncm 15. 0 0. s 10. 4 130 1.30 105 2. s4 7, 540

170 g. enzene. 7 hclmm" 20. 0 0. s 15. 0 112 1.12 05 10.8 0,450

g. to acne. 8 {175 g z l 20. 0 9. 8 10. 8 165 1. 65 10b 4. 62 7,100

175 g 0 none 0 175 g humane 20.0 9.8 10.8 105 1.05 100 0. 41 7,700

Component Parts by Weight Solvent (Benzene and Hexane) 1,080

Styrene 345 Acrylonitrile 1 15 EPDM rubber 63.0 Benzoyl peroxide 4.60

The EPDM rubber was a terpolymer of ethylene, propylene and5-ethylidene-2-norbomene which contained chemically bound thereinapproximately equal weights of ethylene and propylene, and sufficient S-ethylidene 2-norbomene to provide an unsaturation level of ninecarbon-to-carbon double bonds per 1,000 carbon atoms. The EPDM rubberhad an ML-8 (250 F.) Mooney viscosity value of 60. Upon reference Thepercentages of initiator and/0r solvent which were added as incrementsduring the course of the polymerizations were fractional amounts of thetotal quantities in the final mixtures. In the accompanying Table IV, itmay be noted that as many as five incremental additions were made.

After completing a polymerization run, the resulting rubber modifiedplastic product was recovered by steam coagulation, dried and tested.The notched lzod impact value was determined by ASTM D 256-56(one-eighth inch specimen), and the melt flow index was determined byASTM D 123 8-62T (condition G).

Upon referable to the data in Table IV, it may be noted that incrementaladdition results in at least four advantages, as follows:

1. Higher impact strength;

2. A better balance of impact strength and melt flow index properties;

3. A much faster reaction time; and,

4. f more efficient utilization of the initiator.

Some of the more pertinent observations which may be made from a run orgroup of runs appearing in Table IV are given below:

1. Runs 1, 2 and 3 were conducted under standard or basic reactionconditions without incremental addition of solvent or initiator. TheIzod impact value/melt flow index balance and the effect of a higherreaction temperature may be noted. 6

2. Runs 4 and 5 illustrate the effect of incremental addition of solventonly, without changing the ratio of solvent components. There is someimprovement over Runs 1, 2 and 3 in the melt flow index, and the effectof changing the solvent ratio may be noted by comparing this data withthat for Runs 18 and 17.

3. Run 6 illustrates the effects of incremental addition of theinitiator only.

4. Run 7 may be compared with Runs 8-15 to observe the effect ofreaction temperature on the Izod impact value/melt flow index balance.

5. Runs 9, 1O, 12 and 14 illustrate the results that are obtained byincremental addition of solvent without a change in the ratio of solventcomponents. These runs may be compared with the standard reactionconditions illustrated in Runs 1, 2 and 3.

6. Runs 11 and 13 illustrate the upper preferred solvent limit.

7. Runs 17 and 18 illustrate the effect of a change in the ratio ofsolvent components, which results in an improved lzod impact value overthe standard runs.

8. Runs 19 and 20 illustrate the effect of a change in the ratio ofsolvent components in combination with incremental addition of theinitiator.

9. Runs 21 and 22 illustrate the more efficient use of the initiatorwhich is due to incremental addition, with and without a change in theratio of solvent components.

l0. Runs 9, 14, 19 and 21 illustrate that a reduced reaction time ispossible under a variety of conditions when using incremental additionof solvent and/or initiator.

1 1. Runs 9, l3 and 14 illustrate the limits of the times of incrementaladditions where good products are obtained.

l2. Runs 8 and 16 illustrate instances where the time of addition of theincrements was too long for best results.

13. Runs 17 and 18 illustrate the lower initiator limits, and Run 21 theupper.

14. Run 6 illustrates the lower solvent limit, and Runs 11 and 13 theupper solvent limit.

15. Run 17 illustrates the preferred limits in the change in the ratioof solvent components.

16. Runs 15 and 18 illustrate the preferred lower and upper temperaturelimits when benzoyl peroxide is the initiator.

Upon comparing the data in Table IV, it may be noted that an easyflowing rubber modified plastic product is produced by the standardreaction technique illustrated in Runs 1, 2 and 3, but only at aconsiderable sacrifice in impact strength over the optimum obtainable bythe incremental addition technique. It is in this context that the Izodimpact value/melt flow index relation is important. The higher ratios ofthe aliphatic solvent component lead to a higher conversion of themonomers, a lower viscosity for the reaction mixture, a higher molecularweight for the resin component even at high reaction temperatures, and afaster reaction rate. A lower viscosity for the reaction mixture isdesirable as this aids in heat transfer and recovery of the product. Thenormal reaction rate with a 50/50 weight ratio benzene/hexane solvent isabout 10 percent monomer conversion per hours, whereas with a 40/60weight ratio benzene/hexane solvent mixture,

0 the reaction rate rises to as high as 25 percent conversion per hour.

What is claimed is:

l. A plastic composition comprising (A) a resinous polymer selected fromthe group consisting of homopolymers of alkenyl aromatic monomers, vinyland vinylidene halides and homopolymers of acrylic monomers andinterpolymers of alkenyl aromatic TABLE IV Notched Incremental addition,Time izod Benzene/hexane Reaction weight percent incroimpact 1 Meltweight ratio mont(s) (ft.-lbs./ [low 2 Run No. Temp.,0. Time, hrs. BzzOzSolvent added (hrs.) in.) (g./10 min) Initial Final Without IncrementalAddition 1 70 14 None None 4. 4 0. 45 50/50 50/50 2 72 20 None None 4. 20.44 50/50 50/50 3 75 13 None None l. 7 3. 1 50/50 50/50 IncrementalAddition of Solvent Only 4 g8 None as. a a. 2-5. s 3. 5 0. 73 50/50 5050 5 75 15 None 33. 3 2. 8-5. 3 2. 6 2. 4 50/60 50/50 IncrementalAddition of Initiator Only 6 77 38 None 3. 4.0 1. 6 50/50 50/50Incremental Addition of Solvent and Initiator Incremental Addition witha Change in the Solvent Ratio None 33. 3 10. 0 2. 0 1. 1 60/40 40/60None 33. 3 1. 5 6. 1 0. 23 60/40 40/60 None 33. 0 2. 5 8. 3 0. 10 55/4545/55 31. 0 33. 0 3. 0 4. 4 1. 7 55/45 45/55 35. 0 26. 0 3. 5 4. 4 1. 953/47 45/55 Incremental Addition with Reduced Initiator Levels (3.8parts of Benzoyl peroxide) 21 7s 0 52. 0 2e. 0 2. 0-3. 5 4.6 1. 4 50/5050/ 22 7s 30. 0 25. 0 3.5 4. 3 1. 7 53/ 45/55 1 AS'IM D 256-56, inchspecimen.

2 AS'IM D 1238-62T, condition 0.

monomers and acrylic monomers, and (B) a graft interpolymer formed bysimultaneous reaction in solution in an organic solvent of l)elastomeric material consisting essentially of a rubbery interpolymer ofethylene, at least one alpha monoolefin containing 13-16 carbon atomsand 5-ethylidene-2-norbornene, and (2) monomeric material selected fromthe group consisting of alkenyl aromatic monomers, vinyl and vinylidenehalides wherein the halogen content thereof is selected polymerizableorganic solvent which is a solvent for the rubbery interpolymer.

2. The plastic composition of claim 1 wherein the resinous polymer ispolystyrene, and the monomeric 40 material grafted on the interpolymeris styrene.

3. The plastic composition of claim 2 wherein the ratio by weight of thegrafted styrene monomer to the rubbery interpolymer in (B) is betweenabout 1:4 and 4:1, and the plastic composition contains about 1-50 fromthe group consisting of fluorine, chlorine and p rts by weight of therubbery interpolymer for each bromine, acrylic monomers, and mixturesthereof in which the monomers present in the graft polymer are the sameas the monomers of which the resinous polymer (A) is fonned, the alkenylaromatic monomer 99-50 parts by weight of the polystyrene and thegrafted styrene monomer in (B).

4. The composition of claim 3 wherein about 30-120 parts by weight ofthe styrene monomer is grafted on being selected from the groupconsisting of alkenyl aroeach 100 Parts y weight of the rubberyinterpolymer matic hydrocarbons having 8-20 carbon atoms and the halog.iated derivatives thereof, and the acrylic monomer having the generalformula wherein R is selected from the group consisting of hydrogen andalkyl groups having l-5 carbon atoms, and X is selected from the groupconsisting of O O (H) wherein R is an alkyl group containing l-9 carbonatoms, and wherein the organic solvent is a nonin (B), and thecomposition contains about 4-25 parts by weight of the rubberyinterpolymer for each 96-75 parts by weight of the polystyrene and thegrafted styrene monomer in (B).

5. The plastic composition of claim 1 wherein the resinous polymer is aninterpolymer of styrene and acrylonitrile, and the monomeric materialgrafted on the rubbery interpolymer is a mixture of styrene andacrylonitrile.

6. The plastic composition of claim 5 wherein the ratio by weight of thegraftedstyrene and acrylonitrile to the rubbery interpolymer in (B) isbetween about 1:4 and 4:1, the ratio by weight of styrene toacrylonitrile in the overall plastic composition is between about 2:1and 4:1, and theplastic composition contains about l-50 parts by weightof the rubbery interpolymer for each 9950 parts by weight of thestyrene-acrylonitrile interpolymer and the grafted styrene and theacrylonitrile monomer in (B).

7. The plastic composition of claim 6 wherein about 30-120 parts byweight of styrene and acrylonitrile monomer is grafted on each 100 partsby weight of the rubber interpolymer in (B), the ratio by weight ofstyrene to acrylonitrile in the overall plastic composition is about3:1, and the composition contains about 4-25 parts by weight of therubbery interpolymer for each 96-75 parts by weight of thestyrene-acrylonitrile interpolymer and the grafted styrene andacrylonitrile in (B).

8. The plastic composition of claim 1 wherein the monomeric materialincludes a monomer selected from the group consisting of vinyl chlorideand vinylidene chloride.

9. The plastic composition of claim 1 wherein the elastomeric materialis a blend containing 5-95 parts by weight of the said rubberyinterpolymer and -5 parts by weight of a rubbery polymer selected fromthe group consisting of rubbery interpolymers of ethylene and at leastone alpha monoolef'm containing 3-16 carbon atoms, rubbery interpolymersof ethylene and at least one polyene, rubbery interpolymers of isobuteneand at least one polyene, natural rubber, homopolymers of conjugateddiolefins containing 4-10 carbon atoms, and interpolymers of saidconjugated diolefins and at least one monoethylenically unsaturatedmonomer interpolymerizable therewith.

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,683, 050 Dated August 8, 1972 Inventor(s) Curtis L. Meredith et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

column 4, line 25, change "sing" to using column 8, line 45, after"preferred" cancel "1" and substitute monomers column 11, line 31, omit"Upon reference";

column 11, line 44, change "referable" to reference Signed and sealedthis 23rd day of January 1973..

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-iOSO (10-69) USCOMM-DC 60376-P69 U.5, GOVIINMINTPRINTING OFFICE: I!!! 0-36fl-334

2. The plastic composition of claim 1 wherein the resinous polymer ispolystyrene, and the monomeric material grafted on the interpolymer isstyrene.
 3. The plastic composition of claim 2 wherein the ratio byweight of the grafted styrene monomer to the rubbery interpolymer in (B)is between about 1:4 and 4:1, and the plastic composition contains about1-50 parts by weight of the rubbery interpolymer for each 99-50 parts byweight of the polystyrene and the grafted styrene monomer in (B).
 4. Thecomposition of claim 3 wherein about 30-120 parts by weight of thestyrene monomer is grafted on each 100 parts by weight of the rubberyinterpolymer in (B), and the composition contains about 4-25 parts byweight of the rubbery interpolymer for each 96-75 parts by weight of thepolystyrene and the grafted styrene monomer in (B).
 5. The plasticcomposition of claim 1 wherein the resinous polymer is an interpolymerof styrene and acrylonitrile, and the monomeric material grafted on therubbery interpolymer is a mixture of styrene and acrylonitrile.
 6. Theplastic composition of claim 5 wherein the ratio by weight of thegrafted styrene and acrylonitrile to the rubbery interpolymer in (B) isbetween about 1:4 and 4:1, the ratio by weight of styrene toacrylonitrile in the overall plastic composition is between about 2:1and 4:1, and the plastic composition contains about 1-50 parts by weightof the rubbery interpolymer for each 99-50 parts by weight of thestyrene-acrylonitrile interpolymer and the grafted styrene and theacrylonitrile monomer in (B).
 7. The plastic composition of claim 6wherein about 30-120 parts by weight of styrene and acrylonitrilemonomer is grafted on each 100 parts by weight of the rubberinterpolymer in (B), the ratio by weight of styrene to acrylonitrile inthe overall plastic composition is about 3:1, and the compositioncontains about 4-25 parts by weight of the rubbery interpolymer for each96-75 parts by weight of the styrene-acrylonitrile interpolymer and thegrafted styrene and acrylonitrile in (B).
 8. The plastic composition ofclaim 1 wherein the monomeriC material includes a monomer selected fromthe group consisting of vinyl chloride and vinylidene chloride.
 9. Theplastic composition of claim 1 wherein the elastomeric material is ablend containing 5-95 parts by weight of the said rubbery interpolymerand 95-5 parts by weight of a rubbery polymer selected from the groupconsisting of rubbery interpolymers of ethylene and at least one alphamonoolefin containing 3-16 carbon atoms, rubbery interpolymers ofethylene and at least one polyene, rubbery interpolymers of isobuteneand at least one polyene, natural rubber, homopolymers of conjugateddiolefins containing 4-10 carbon atoms, and interpolymers of saidconjugated diolefins and at least one monoethylenically unsaturatedmonomer interpolymerizable therewith.